1. Field of the Invention
The present invention relates to an interactive information distribution system such as a video-on-demand (VOD) system. More particularly, the present invention relates to a method and apparatus for masking the effects of latency within such an interactive information distribution system.
2. Description of the Background Art
Recent advances in digital signal processing techniques and, in particular, improvements in digital compression techniques, have led to a plethora of proposals for providing new digital services to a subscriber's home via existing telephone and coaxial cable networks. For example, it has been proposed to provide hundreds of cable television channels to subscribers by compressing digital video, transmitting the compressed digital video over conventional coaxial cable television channels, and then decompressing the video at a subscriber's set top terminal. Another proposed application of this technology is a video-on-demand system in which a subscriber communicates directly with a video service provider via telephone lines to request a video program from a video library and the requested video program is routed to the subscriber's home via telephone lines or via coaxial cable television cables for immediate viewing. Other proposed video-on-demand systems use a frequency multiplexing technique to enable control information from a set top terminal to be transmitted through a cable network back to an information server. Such a system permits bi-directional communications between the service provider and the subscriber over a single network.
In each of these information distribution systems, the compression and decompression techniques as well as processing of control information requires a substantial amount of time. As such, a customer experiences a significant delay or latency between the selection of a function via their set top terminal and when the selected function is actually implemented upon the screen of their television. Heretofore this latency has merely been an annoyance which, for the most part, has been ignored by the interactive information distribution system providers. Typically, upon selection of a certain function, such as stop or pause, while viewing a particular video stream, the present systems merely delay the time of implementing that stop or pause function by the amount of latency. The latency can be in excess of five seconds. Furthermore, if a customer has a particular video stream being displayed and then selects a second video stream for display, present systems, after a slight control signal processing delay, switch from one video stream to another video stream without any attempt to smooth the transition. As such, the video that is received and decoded by the user's set top terminal is generally garbled or distorted during the transition period. If a customer is rapidly switching from video stream to video stream, e.g., channel surfing, the customer will view garbled video images for a substantial amount of time between "channel" changes. Such an extended period of garbled images is unacceptable for a commercial system.
Therefore, there is a need in the art for a method and apparatus for masking the effects of latency in an interactive information distribution system.